1. Technical Field
The present invention relates to a digital subscriber line (DSL) multiplexer for providing connectivity to a data network. In particular, the present invention involves the exchange of management information from the DSL multiplexer to an end-user DSL modem.
2. Background Art
As the information age matures, it is enabled by a number of technological advances, such as the geometric growth of networked computing power and the prevalence of reliable and ubiquitous transmission media. Today""s consumers in both the residential and business arena have been acclimated to a more graphical approach to communication. In particular, multimedia applications (which include textual, graphical, image, video, voice and audio information) have become increasingly popular and find usage in science, business, and entertainment. Local area networks (LANs) are essential to the productivity of the modem workplace; Ethernet-type networks have dominated the LAN market and have been continually enhanced (e.g., switched Ethernet, Fast Ethernet, and/or Gigabit Ethernet) to keep pace with the bandwidth intensive multimedia applications.
A compelling example of the growth of information consumption is the dramatic increase in users of the World Wide Web, a multimedia-based information service provided via the Internet. Although initially a forum for academia to exchange ideas captured in ASCII text, the Internet has developed to become a global media for users from all walks of life. These Internet users regularly exchange multimedia graphical, image, video, voice and audio information as well as text.
Furthermore, the business world has come to realize tremendous value in encouraging workers to telecommute. To avoid the idle commuting time, today""s workers enjoy the convenience of working from home via their personal computers. As illustrated in FIG. 1A, a user at a remote site 101 (e.g., home) has traditionally been able to access her/his office 119, which includes accessing an office local area network 119b (LAN), through a dial-up connection over a 33 Kbps or 56 Kbps modem 101b. The dial-up connection is handled by a telephone communication facility 240 (CO) 105 through a voice switch 107, which switches the xe2x80x9cdataxe2x80x9d call through a public switched telephone network (PSTN) 111. The data call terminates in a remote CO 121 at a voice switch 123. The voice switch 123 switches the call to the subscriber; in this case, the called line is associated with a modem in a modem pool 119a. Once connected to the modem pool 119a, the end user at her/his remote site 101 can access the computing resources in his office 119. These sources include a multimedia server 119c and a PC 119d of the remote user. A similar connection to Internet 115 by a user at a remote site 101 can be accomplished by connecting to an Internet Service Provider (ISP) 117 instead of modem pool 119c. 
Unfortunately, telecommuting from a remote office or accessing multimedia information from home over the Internet imposes an enormous strain on networking resources. It is common knowledge that the networking infrastructure is the bottleneck to the expedient transfer of information, especially bandwidth intensive multimedia data. As alluded to before, today""s access methods are limited to standard analog modems, such as 101b, which have a maximum throughput of 56 Kbps on a clean line (i.e., a line not having any appreciable noise causing errors in bit rate transfer). Remote users may alternatively acquire basic rate (2B+D) Integrated Services Digital Network (ISDN) services at 128 kbps. Even at this speed, telecommuters may quickly grow impatient with slow response times as compared to the throughput of their LANs to which they have grown accustomed. On average, a typical Ethernet user can expect to achieve approximately 1 Mbps on a shared 10Base-T Ethernet LAN and up to 9+Mbps in a full duplex switched Ethernet environment. In addition, Internet users are also demanding greater access speeds to cope with the various multimedia applications that are continually being developed. Fortunately, the communication industry has recognized the escalating demand.
Cell switching technology, such as Asynchronous Transfer Mode (ATM), was developed in part because of the need to provide a high-speed backbone network for the transport of various types of traffic, including voice, data, image, and video. An ATM network 113 is typically able to provide bandwidths to an ATM user at approximately 1.5 Mbps on a T1 line, 44.7 Mbps on a T3 line, and 155 Mbps over a fiber optic OC-3c line. Consequently, ATM networks are suitable to transport multimedia information.
ATM further provides a mechanism for establishing quality of service (QoS) classes during the virtual channel setup, thereby allotting a predetermined amount of bandwidth to the channel. QoS classes define five broad categories that are outlined, for example, by the ATM Forum""s UNI 3.0/3.1 specification. Class 1 specifies performance requirements and indicates that ATM""s quality of service should be comparable with the service offered by standard digital connections. Class 2 specifies necessary service levels for packetized video and voice. Class 3 defines requirements for interoperability with other connection-oriented protocols, particularly frame relay. Class 4 specifies interoperability requirements for connectionless protocols, including IP, IPX, and SMDS. Class 5 is effectively a xe2x80x9cbest effortxe2x80x9d attempt at delivery; it is intended for applications that do not require guarantees of service quality.
In conventional data networks, such as the typical Ethernet LAN or X.25 WAN, there are no explicit negotiations between the network and the user specifying the traffic profile and quality of service expected. Rather, the network is expected to provide each user with a xe2x80x9cfair sharexe2x80x9d of the available bandwidth.
However, in an ATM network, fair allocation of bandwidth requires users to adjust their transmission rates according to the feedback from the network. ATM networks carry fixed bandwidth services required for multimedia applications (constant bit rate (CBR) traffic) and guaranteed bandwidth services for high-priority data applications (variable bit rate (VBR) traffic). The remaining bandwidth, not used by guaranteed bandwidth services, must be shared fairly across all users. The ATM Forum refers to services that make use of this otherwise idle bandwidth as available bit rate (ABR) services.
Although these ABR applications must contend for remaining available bandwidth and would not provide specific throughput guarantees, ABR applications still would require fair access to the available bandwidth with a minimum of cell loss. If ABR traffic had no mechanism to determine if sufficient bandwidth were available to handle the transmission on the network and traffic was simply fed in, network congestion might result in dropped cells, and application traffic might be lost. ABR flow control is an ATM layer service category for which the limiting ATM layer transfer characteristics provided by the network may change after establishing the network connection. A flow control mechanism is specified which supports several types of feedback to control the source rate in response to changing ATM layer transfer characteristics. When the network becomes congested, the end-stations outputting ABR traffic are instructed to reduce their output rate. It is expected that an end-system that adapts its traffic in accordance with the feedback will experience a low cell loss ratio and obtains a fair share of the available bandwidth according to a network-specific allocation policy. Cell delay variation is not controlled in this service, although admitted cells are not delayed unnecessarily.
In this end-to-end rate-based scheme, the source (e.g., a user remote site 103) of a virtual circuit (VC) indicates the desired rate in a resource management cell (RM cell). An RM cell is a standard 53-byte ATM cell used to transmit flow-control information. The RM cell travels on the VC about which it carries information, and is therefore allowed to flow all the way to the destination end-station (e.g., PC 119d ). The destination reflects the RM cell, with an indicator to show that the RM cell is now making progress in the reverse direction. The intermediate switches (e.g., switch 109) then identify within the reverse RM cell their respective maximum rates (the explicit rate allocated to the VC). After the source receives the reverse RM cell, the smallest rate identified in the reverse RM cell is then used for subsequent transmissions until a new reverse RM cell is received.
ATM has many recognized advantages and has dominated wide area networks (WANS) as the preferred backbone transport technology. Because of cost and performance factors, ATM faces stiff competition from both switched and shared-media high-speed LAN technologies, including Ethernet, Fast Ethernet, and Gigabit Ethernet. And although ATM typically offers QoS guarantees superior to the prioritization schemes of competing high-speed technologies, many users remain unable to take advantage of these features. If a remote user wishes to obtain the advantages of ATM, one solution would be to acquire an ATM switch on the premises as shown in FIG. 1A. The remote site 103 would need to be equipped with an ATM switch 103a, whereby a PC 103b interfaces the ATM switch 103a via an ATM NIC 103c. In addition, the remote user would have to lease a T1 line or an OC-3c pipe from the Telco. The leased line would terminate in an ATM switch 109 in the CO 105. The CO ATM switch 109 is connected to the ATM network 113. With an ATM connection, the remote user may quickly access multimedia information on the Internet by establishing a virtual channel that would terminate at ATM switch 125 in CO 121. The CO 121 would of course have some means of communication with the ISP 117; typically routers (not shown) are used.
Alternatively, FIG. 1B illustrates an ATM to the desktop solution whereby the xDSL technology is utilized to extend ATM capability remotely. At the customer premises 103, a PC 103b is equipped with an ATM NIC 103c, which is attached to an xDSL modem 103d. In addition, a telephone set 103e is linked to the xDSL modem 103d. The xDSL modem is connected over twisted pair copper wire to the CO 105, terminating at the POTS splitter 117. The POTS splitter 117 separates the data signals originating from the PC 103b from the voice signals. A xDSL multiplexer (mux) 115 receives the data signals from the POTS splitter and uplinks these signals to the ATM switch 105. Although the solution present above provides a way to deliver ATM capabilities to the desktop, it disadvantageously requires the acquisition of ATM NICs by the remote users, and the xDSL modem has to have a costlier ATM interface.
Despite all the many inherent advantages with ATM, Ethernet-type LANs constitute nearly all of the networking resources of business and residential users. Moreover, these legacy systems are still being enhanced and marketed, e.g., switched Ethernet, switched Fast Ethernet, and switched Gigabit Ethernet are significantly lower cost than their ATM counterparts. ATM technology requires a substantial investment in infrastructure, from cable plant to switches to network interface cards (NICs). This tremendous investment cost can be sustained in the wide area network (WAN) where costs can be spread out. However, in the LAN environment, the investment in infrastructure is typically unsustainable which translates into retention of xe2x80x9clegacyxe2x80x9d LANs such as Ethernet.
While a number of service providers (e.g., Telcos) employ ATM to establish point-to-point circuits, little has been done to utilize ATM for transporting multimedia information or services to the desktop. This is simply not commercially practical. As previously noted, commercial practicality prohibits such an endeavor. In essence, millions of users would be required to purchase expensive ATM network interface cards, and then possibly add very costly T1, T3, or OC-3c lines. As a result, service providers have not commercially implemented ATM in the delivery of multimedia information to the desktop.
One apparent disadvantage is the inability of current access techniques to adequately provide bandwidth to the end user for access to networking resources.
Another disadvantage is the high cost related to procuring sufficient bandwidth to alleviate long delays caused by low speed connection.
There is a need for an arrangement that enables the high-speed transmission of multimedia information to the desktop.
There is also a need for an arrangement that enables use of an Ethernet-type network interface device to access a high speed cell switching network.
There is also a need for an arrangement that ensures reliable connectivity to networking resources.
These and other needs are attained by the present invention, where a digital subscriber line (DSL) multiplexer employs a proprietary protocol to communicate with an end user DSL modem to monitor the connection.
According to one aspect of the present invention, a multiplexing device for providing high speed network connectivity for the transport of data frames to at least one subscriber, comprises a digital subscriber line (DSL) transceiver interface coupled to plurality of subscriber DSL modems. A packet buffer is coupled to the DSL transceiver interface for storing the data frames. The packet buffer transfers the data frames over a packet buffer bus. An Ethernet-type port is coupled to the packet buffer for uplinking to an external switch. A central processing unit (CPU) is coupled to the packet buffer for executing code to send and receive proprietary protocol packets for communicating management information associated with the plurality of subscriber DSL modems. The management information indicates presence of an Ethernet-type port, current line speed, and media access control (MAC) address.
Additional advantages and novel features of the invention will be set forth in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.